No call of constructor of singleton

I have singleton class, intended to for use in one thread (GUI thread), to protected from wrong usage I add assert

//header file
class ImageCache final {
public:
    ImageCache(const ImageCache &) = delete;
    ImageCache &operator=(const ImageCache &) = delete;
    static ImageCache &instance()
    {
       static ImageCache cache;
       return cache;
    }
    void f();
private:
    QThread *create_context_ = nullptr;
    ImageCache();
};

//cpp
ImageCache::ImageCache()
{
    create_context_ = QThread::currentThread();
    qInfo("begin, cur thread %p\n", create_context_);
}

void ImageCache::f()
{
    assert(create_context_ == QThread::currentThread());
}

all works fine, but on one machine there is assertion failure in ImageCache::f, I have no direct access to that machine (hence this question).

The interesting thing, that according to log ImageCache::ImageCache was not called at all, and assert failed because of

assert(0 == QThread::currentThread());

I move implementation of ImageCache::instance from header file to .cpp file, send updated source code to user of these machine (on my all works fine), he rebuilds and all start works as expected.

I ask him for compiled binaries (with assert failure and without) the only difference between them is place of ImageCache::instance implementation,

and compare assembler.

there is no difference between calls of ImageInstance::instance().f() at all, and there is one difference in disassembler of ImageInstance::instance,

the failure one looks like this:

 static ImageCache &instance()
   4938f:   55                      push   %rbp
   49390:   48 89 e5                mov    %rsp,%rbp
   49393:   41 54                   push   %r12
   49395:   53                      push   %rbx
    {
        static ImageCache cache;
   49396:   48 8b 05 bb db 23 00    mov    0x23dbbb(%rip),%rax        # 286f58 <_ZGVZN10ImageCache8instanceEvE5cache@@Base-0x2150>
   4939d:   0f b6 00                movzbl (%rax),%eax
   493a0:   84 c0                   test   %al,%al
   493a2:   0f 94 c0                sete   %al
   493a5:   84 c0                   test   %al,%al
   493a7:   74 5c                   je     49405 <_ZN10ImageCache8instanceEv+0x76>
   493a9:   48 8b 05 a8 db 23 00    mov    0x23dba8(%rip),%rax        # 286f58 <_ZGVZN10ImageCache8instanceEvE5cache@@Base-0x2150>
   493b0:   48 89 c7                mov    %rax,%rdi
   493b3:   e8 08 b7 fe ff          callq  34ac0 <__cxa_guard_acquire@plt>

the good one is looks like this:

ImageCache &ImageCache::instance()
{
   50c12:   55                      push   %rbp
   50c13:   48 89 e5                mov    %rsp,%rbp
   50c16:   41 54                   push   %r12
   50c18:   53                      push   %rbx
    static ImageCache cache;
   50c19:   0f b6 05 98 94 23 00    movzbl 0x239498(%rip),%eax        # 28a0b8 <_ZGVZN10ImageCache8instanceEvE5cache>
   50c20:   84 c0                   test   %al,%al
   50c22:   0f 94 c0                sete   %al
   50c25:   84 c0                   test   %al,%al
   50c27:   74 50                   je     50c79 <_ZN10ImageCache8instanceEv+0x67>
   50c29:   48 8d 3d 88 94 23 00    lea    0x239488(%rip),%rdi        # 28a0b8 <_ZGVZN10ImageCache8instanceEvE5cache>
   50c30:   e8 cb 3d fe ff          callq  34a00 <__cxa_guard_acquire@plt>

The difference is

//bad
mov    0x23dbbb(%rip),%rax 
movzbl (%rax),%eax
//good
movzbl 0x239498(%rip),%eax

I interpret this, that for some reason %eax register from the first one variant got wrong value, and because of this got decision that global object was initialized while it is not initialized. In the second case all works as expected.

So is it compiler failure (gcc (Ubuntu 7.3.0-27ubuntu1~18.04) 7.3.0 / amd64 / linux) or I should use ImageCache::instance inside .cpp for some reason, or some other reason that cause difference code generation, like some compiler falgs may cause this failure? Code was compiled with -O0 -std=c++11